Item: A REVIEW OF AVALANCHE RELEASE MECHANISMS: FROM ANTICRACK PROPAGATION TO SUPERSHEAR FRACTURE
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Title: A REVIEW OF AVALANCHE RELEASE MECHANISMS: FROM ANTICRACK PROPAGATION TO SUPERSHEAR FRACTURE
Proceedings: Proceedings, International Snow Science Workshop, Whistler, BC, Canada, 2026
Authors:
- Johan Gaume [ WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland ] [ ETH Zurich, Switzerland ] [ Climate Change, Extremes and Natural Hazards in Alpine Regions Research Centre CERC, Davos, Switzerland ]
- Alec van Herwijnen [ WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland ]
- Jürg Schweizer [ WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland ]
Date: 2026-09-28
Abstract: Dry-snow slab avalanches are responsible for most avalanche fatalities, making understanding of release mechanisms essential for forecasting and hazard assessment. Slab avalanche release is now understood as a sequence of coupled mechanical processes: failure initiation in a buried weak layer, onset of crack propagation, dynamic crack propagation, and ultimately slab fracture, crack arrest, and release. Over decades of research, conceptual models of avalanche release have emerged, ranging from weak layer shear failure to collapse-driven anticrack propagation, often treated as competing explanations. In this review, we bring together laboratory experiments, field observations, numerical simulations, and analytical models, from which a unified perspective on slab avalanche release emerges. Across these approaches, consistent evidence shows that the type of crack propagation depends on the situation, in particular slope angle. On gentle terrain and in propagation saw tests, propagation is typically slow (< 60 m s⁻¹), associated with weak layer collapse and slab bending. On steep slopes, the propagating crack can accelerate and become dominated by weak layer shear failure, with characteristics consistent with supershear fracture. Crack speeds may then exceed the slab shear wave velocity (> 100 m s⁻¹). This suggests that these two propagation regimes, collapse-driven and shear-dominated, appear to describe different situations of the same dynamic process. The relative importance of collapse and shear depends on slope angle, the resulting stress state, and the weak layer failure envelope. Together, these findings help reconcile previously competing theories of avalanche release and highlight the need to consider both collapse-driven and shear-dominated crack propagation regimes. Further work is needed to assess whether this framework applies to natural avalanche release, or whether slab viscoelastic relaxation or weak layer ductile-to-brittle transition lead to partly different release mechanisms.
Object ID: ISSW2026_O1.1.pdf
DOI: https://doi.org/10.15788/1790098467
Language of Article: English
Presenter(s): Johan Gaume
Keywords: dry-snow slab avalanche, avalanche release, weak layer, failure initiation, crack propagation, anticrack, supershear fracture, slab fracture.
Page Number(s): 291 - 298
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